Motherboard Chipset

What does your Motherboard Chipset actually do?

We have all heard about the latest chipsets from Intel, VIA, Nvidia, SiS and more and how much better they are. But what does the chipset actually do on the motherboard? We know what the CPU does, we know what the graphics card is for and why we have a hard disk drive but not many people know too much about the chipset. Hopefully we can shed a little light on the working of the chipset and why they differ from one chipset to the next.

North and South bridge?

The chipset normally consists of two major microchips. These are known as the North bridge and the South Bridge. Developments in chip technologies have meant that chipset and CPU manufacturers are changing the way the chipset layout works, for example some CPU’s come with a built in memory controller taking that job from the North Bridge, some chipsets have incorporated the north and south bridge in the same chip, but for now we will look at the standard setup.

The North Bridge Handles data for the graphics port whether that be AGP or PCI express and the main memory which includes the FSB (Front side bus). Although both chips are required for the PC to work the North Bridge handles most of the very important tasks such as the connection between the CPU and main memory bank. The South Bridge handles data from the PCI x1 slots and can also have integrated components such as Audio and/or onboard graphics.

The North and South bridges will have different chip names even though they are very often paired with the same opposite bridge to come under the collective name of the chipset. Below is a diagram of the KT600 chipset from VIA technologies.

This diagram shows how the components of your PC are connected to the chipset.

Chipset diagram

Catch the Bus

The function of a chipset is to manage data throughput. All data that your components require or acquire need to be transported. They are transported by what’s known as a bus. The bus carry’s the data to where it needs to go via the chipset. The exception to rule here is the BSB (Back side bus) the BSB is the bus between the CPU and the cache memory. Today’s CPU’s have the cache memory “on-chip” and so there is no need to go through the chipset.

The BSB is not to get confused with the main memory bus. The BSB only dictates the speed between the CPU and the cache memory. The memory bus speed is on a different bus and this speed can be changed independently. Excluding the BSB all other buses go through the chipset in order to get direction for where it needs to take the data. Because of the amount of data that goes through the chipset it is important that the chipset is up to speed. This is one of the components that often gets overlooked but a poor performing chipset can severely hamper your computers performance.

Modern chipsets have a dedicated bus in order to communicate between the north and south bridge, before the PCI bus was used but this was getting crowded as many components demanded more on more of the available bandwidth. The solution was this dedicated bus that only ran between the north and south bridge. Different companies used different names for this connection between the
bridges, Intel’s solution was called DMI (Direct Media Interface). Nvidia and ULi called theirs HyperTransport, and VIA went with V-Link. Essentially however the solutions were all very similar.

What Chipset?

Since we now know that the chipset handles an incredible amount of data, its important to see which chipsets are performing the best. Firstly to choose a chipset that supports your CPU. You obviously cant have a chipset designed for an Intel CPU if your using a AMD based CPU of course the motherboard you buy will clearly display which model of CPU it is for. Then the best way to see which chipsets are performing the best is to look at benchmarks on various internet sites. A slow chipset can be as damaging to your systems overall speed as a slow CPU or slow memory. The slowest component always dictates the overall speed at any given time. If you have a poor performing chipset, then any time that your computer is sending and receiving data from the graphics card or main memory, then the system is struggling.

Does it affect your graphics speed?

Like stated above the the chipset is responsible for directing data from the AGP/PCI 16x bus. So it does affect the graphics performance of your machine. But it also affects it in another way if your using an older AGP card. You may notice that when you purchase a graphics card it will state on it what AGP Bus it can use i.e. 1x, 2x, 4x or 8x. This is how many channels the AGP bus can use to transmit data from the graphics card to the main memory. Support from the chipset to have 8 channels to the graphics card allows the graphics card to transmit greater amounts of data per second.

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